21211243 has 4 divisors (see below), whose sum is σ = 21262048. Its totient is φ = 21160440.

The previous prime is 21211237. The next prime is 21211247. The reversal of 21211243 is 34211212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21211243 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21211247) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 24771 + ... + 25612.

It is an arithmetic number, because the mean of its divisors is an integer number (5315512).

Almost surely, 2^21211243 is an apocalyptic number.

21211243 is a deficient number, since it is larger than the sum of its proper divisors (50805).

21211243 is an equidigital number, since it uses as much as digits as its factorization.

21211243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50804.

The product of its digits is 96, while the sum is 16.

The square root of 21211243 is about 4605.5665232412. The cubic root of 21211243 is about 276.8144177826.

Adding to 21211243 its reverse (34211212), we get a palindrome (55422455).

It can be divided in two parts, 2121 and 1243, that added together give a square (3364 = 58²).

The spelling of 21211243 in words is "twenty-one million, two hundred eleven thousand, two hundred forty-three".